Septins are GTP-binding and filament-forming proteins found ubiquitously in the eukaryotic lineage that spans from yeasts to humans. Septins participate in cellular processes that involve remodeling of membranes and cytoskeletal structures, especially during cell division and cytokinesis. In budding yeast (Saccharomyces cerevisiae), septin filament assembly serves a prominent role in coordinating cell cycle events, in part, by establishing a scaffold for recruitment and interaction of numerous protein kinases at the developing interface (bud neck) between a mother cell and its daughter cell. Hsl1, a member of the family of AMPK-related protein kinases, is located at the bud neck and is integrally involved in coupling septin collar assembly to licensing of entry into M phase. This proposal describes experimental approaches to address three areas of Hsl1-mediated signaling that are currently poorly understood: (1) What factors are necessary for Hsl1 activation? (2) What role does Hsl1-mediated phosphorylation of new and established targets play in exit from the checkpoint? (3) What function does the ubiquitin-associated domain (DBA) of HsM play in its activity, localization, and/or stability? [unreadable] [unreadable] [unreadable]